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A majority of U.S. children may have vitamin D levels that are too low, and worrisome health problems in adolescence might also be linked to low vitamin D. Those are the findings in this week's online version of the journal Pediatrics.
Here's NPR's Patty Neighmond.
PATTY NEIGHMOND: There's been some evidence that vitamin D not only helps build bones but also helps build the immune system and may even guard against heart disease. Most of that research has been about vitamin D levels in adults. Now some researchers are turning their attention to children. In one new study, researchers looked at federal health statistics on children between the ages of one and 21. They determined that nine percent of them were deficient in the vitamin. That's nearly eight million children. Another 60 percent of children, about 51 million, had levels of vitamin D that were lower than what some doctors consider optimal.
Dr. Michal Melamed is a kidney specialist with New York's Albert Einstein College of Medicine and she headed the study.
Dr. MICHAL MELAMED (Kidney Specialist, Albert Einstein College of Medicine): After we turn 30, we start losing bone. And so, if so many of our young children don't have enough vitamin D, you know, potentially were not actually reaching the peak bone mass that we should be reaching. And in 60 years, there will probably a lot more osteoporosis.
NEIGHMOND: But it's not just future bone health that may suffer when children grow up with too little vitamin D. A second study in the journal focused on teenagers. Researcher Jared Reis with the National Heart, Lung and Blood Institute.
Dr. JARED REIS (Researcher, National Heart, Lung, and Blood Institute): Adolescents with the lowest levels of vitamin D appear to have about two times the risk of high blood pressure, of having hyperglycemia or high blood glucose levels and about four times the risk of metabolic syndrome, as compared to adolescents who had the highest levels of vitamin D, suggesting that vitamin D may play some role in the development of these conditions.
NEIGHMOND: But Reis says these studies were preliminary and not designed to confirm whether low vitamin D actually causes these health problems. To answer that, he says, more studies have to be done. And in January, researchers begin recruiting 20,000 adults to take part in a large scientific trial of vitamin D, along with omega 3 fatty acids. Dr. Joann Manson directs preventive medicine at Brigham and Women's Hospital and is one of the study's principal investigators. She cautions against jumping on the megadose vitamin D bandwagon until research yields some definitive answers.
Dr. JOANN MANSON (Director of Preventive Medicine, Brigham and Women's Hospital): And what's particularly exciting is that vitamin D may have a role in reducing some of the health disparities that are seen by race and ethnicity, because it is known that African-Americans tend to have higher risk of vitamin D deficiency, and they also have a higher frequency of diabetes, hypertension, heart failure.
NEIGHMOND: Darker skin pigment inhibits the body's ability to synthesize vitamin D from the UV rays of the sun. Researchers say if it does turn out that vitamin D in fact has dramatic health benefits, then deficiencies can be solved fairly simply. For starters, Dr. Michal Melamed says parents can offer children foods high in vitamin D.
Dr. MELAMED: Things like sardines, and salmon and tuna have vitamin D in them naturally. And older people will remember taking cod liver oil, which is very rich in vitamin D.
NEIGHMOND: But if kids don't find those foods appealing, then says Melamed, parents can offer breakfast cereals, milk and orange juice, which are all fortified with vitamin D. Right now, federal guidelines suggest only 200 international units of vitamin D for everyone up to 50 years old, but the government's now reviewing that number. The American Academy of Pediatrics one year ago doubled its recommendation for children to 400 international units a day, a common dose now found in vitamins for children.
Patty Neighmond, NPR News.
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